The present invention relates to security locks for building portals such as doors.
It is desirable to be able to secure a door against unauthorized entry, while still being able to open the door enough to view/inspect a person or speak to them. Door chains perform that function, but are subject to being dislodged by strong pressure exerted against exterior of the door. That is, the chain is attachable between a pair of fixtures which are screwed to the door and door jam. The screws are oriented horizontally, i.e. parallel to the direction of the external impact applied to the door. Subsequently the screws can be pulled from their holes under the force of the impacts.
It is therefore, the object of the present invention to minimize or obviate shortcomings of the type discussed above.
In addition, another object is to provide a locking device for a building portal, such as a door, which enables the door to be opened only slightly and yet is highly resistant to external forces applied to the door.